Live Long, Live Well: Quantifying the Health of Heterogenous Populations

Various health-, quality-, and disability-adjusted life year or life expectancy (HALY, QALY, DALY; HALE, QALE, DALE) measures have become gold standards for defining outcomes in technology evaluation, population health monitoring, and other evaluative efforts. As such, it is critical that the analytical framework within which these measures are used for descriptive and evaluative purposes be theoretically consistent and statistically rigorous. For instance, widely-accepted definitions of cost-effectiveness ratios and other technology evaluation criteria that are based on expectations of the respective cost and outcome measures must as such be defined in terms of expected HALYs or QALYs. Similarly, measures like HALEs or QALEs used for population health monitoring are typically concerned with population expectations of such measures (or their corresponding totals). This paper demonstrates that estimation of such expectations necessarily requires consideration of the population variation in and covariation between quality and longevity. From the perspective of several different environments characterizing such heterogeneity, quantification or estimation of measures like QUALs are recondidered. An empirical example of the central issues is provided by means of an analysis of the Years of Healthy Life (YHL) measure drawn from the U.S. National Health Interview Survey.